gh-84538: add strict argument to pathlib.PurePath.relative_to (GH-19813)

By default, :meth:`pathlib.PurePath.relative_to` doesn't deal with paths that are not a direct prefix of the other, raising an exception in that instance. This change adds a *walk_up* parameter that can be set to allow for using ``..`` to calculate the relative path.

example:
```
>>> p = PurePosixPath('/etc/passwd')
>>> p.relative_to('/etc')
PurePosixPath('passwd')
>>> p.relative_to('/usr')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "pathlib.py", line 940, in relative_to
    raise ValueError(error_message.format(str(self), str(formatted)))
ValueError: '/etc/passwd' does not start with '/usr'
>>> p.relative_to('/usr', strict=False)
PurePosixPath('../etc/passwd')
```


https://bugs.python.org/issue40358

Automerge-Triggered-By: GH:brettcannon

1 files changed, 1 insertions, 0 deletions

diff --git a/Misc/ACKS b/Misc/ACKS
index 9853148..5d97067 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1440,6 +1440,7 @@ Pierre Quentel
 Brian Quinlan
 Anders Qvist
 Thomas Rachel
+Domenico Ragusa
 Ram Rachum
 Jeffrey Rackauckas
 Jérôme Radix